A power conversion device including a power module having a power semiconductor module housed in a metal-made case having a heat dissipating unit, has been known. For example, electric vehicles, such as electric motor vehicles or hybrid motor vehicles, are equipped with this type of power conversion device.
The power semiconductor module is sealed with resin in a state where both front and back surfaces of a power semiconductor element have been soldered to conductive plates and electrode terminals have been exposed. The metal-made case has heat dissipating units to be attached to the respective conductive plates with an insulating adhesive having thermal conductivity, on both sides thereof. Each of the heat dissipating units includes a plurality of fins for dissipating heat, formed thereon. The metal-made case has a bottomed-can-shape including an opening on the side of one side end portion, with a flange portion. The power semiconductor module is housed in the metal-made case in a state where the electrode terminals of the power semiconductor element have been inserted through the opening of the metal-made case.
This metal-made case has a structure having a frame and two fin plates each including the plurality of fins formed, joined to each other. The frame includes openings facing front and back surfaces of a circuit body including the power semiconductor elements sealed with the adhesive, formed thereon. The openings include the pair of fin plates each having the plurality of fins, arranged and joined therein (for example, refer to PTL 1).
In this type of power semiconductor device, it is necessary to release heat generated by the power semiconductor element during conducting operation, to the exterior through a heat dissipating member. Therefore, when tensile stress occurs in the insulating adhesive under operating conditions in which thermal cycles are loaded, there is a risk that detachment occurs at a coupling interface. Therefore, a technique of causing compressive stress to remain in the insulating adhesive, has been disclosed (for example, refer to PTL 2).